1. Field of the Invention
The present invention relates to medical syringes and more particularly to an automatic rotary cam actuated syringe apparatus that can inject medicines and the like from removable cartridges (including single chamber and/or dual chamber syringes). Even more particularly, the present invention relates to an improved cam operated syringe that uses a cartridge that is pushed into a handle portion of the apparatus. The cam forces down and projects a needle, subsequently a plunger that ejects the medicine or drug, and wherein when the cam completes its rotation the inner barrel retracts so that the needle is no longer exposed.
2. General Background
Automatic syringes are used to administer parenteral medications to patients under emergency and routine situations. Urgent situations include, for example, military personnel who must administer analgesics, antibiotics or nerve gas antidotes under battlefield conditions. Persons who have severe allergies require immediate injections of epinephrine or glucocorticoids to prevent anaphylaxis. Sumatriptan or dihydroergotamine are frequently self-administered by migraineurs for immediate relief of headaches. Glucagon is often self-injected to counteract hypoglycemia in insulin dependent brittle diabetics.
Repetitive, non-urgent, use of automatic syringes is also common. Patients with chronic or prolonged medical conditions must often self-inject medications on a daily basis. Such injections include insulin by diabetics, low molecular weight heparin by patients predisposed to deep vein thrombosis, menotropins by infertile patients, growth hormone by short statured children, interferon beta-1a for multiple sclerosis, glucocerebrosidase-.beta.-glucosidase for Gaucher's Disease and numerous other injectable drugs for anti-cancer therapy, analgesia and male erectile dysfunction.
While self-injection therapies are cost effective, many patients do not initiate such treatments. The most common reason self-injection with an automatic syringe is not widely accepted is needle phobia. An estimated 10% to 27% of the population have an unfounded fear of hypodermic needles. In such persons, fear and avoidance behavior is triggered by visual exposure to the needle. It is known that needle phobia can be minimized or overcome by hiding the needle before, during and after the injection procedure.
Various types of automatic syringes for administering parenteral medications are known. In my prior art U.S. Pat. No. 5,267,963, there is disclosed a cam operated syringe that has a transversely extended upper end housing, a sliding cam member that is spring loaded to first expose the syringe needle and then dispense the syringe contents. While my former patent provides for a hidden needle to penetrate, inject medication and retract the needle, it does not provide for a more compact design of a rotary cam nor for removal and replacement of a spent medication syringe. There is no concept for reactivating the device for repeat use.
Other automatic syringes have additional problems. Specifically, all reusable automatic syringe devices require the medication containing cartridge to be completely enclosed into the device, remounted with a cover, needle uncapped and other nuances before repeat use. For example, the recently released automatic syringe, Genotropin.TM., requires a total of twenty-three steps to remove a spent syringe cartridge, reload and automatically inject another medication. Such problems make home injection therapy particularly difficult in older patients who may be inept, possess manual tremors, have a loss in manual dexterity or possess other physical impairments. Another problem facing the user of a syringe is that of contamination. Contamination can in fact be in the form of a disease communicated from a patient to a doctor or a nurse if a syringe is contaminated and then carelessly handled. Needle recapping, or other accidental needle stick injury by persons exposed to contaminated needles from hepatitis or AIDS patients can have serious legal and life threatening consequences.
What is needed is a compact automatic syringe that will eliminate accidental contaminated needle stick injuries, overcome needle phobia, and remain user friendly by it's simplicity of use. In view of the foregoing, increased use of home health care for cost containment, and increasing use of bioengineered recombinant DNA drugs that are proteins and must be administered by injection, there is a need for a simple, re-usable and affordable automatic syringe.
Publications that discuss the problems of needlestick include, for example, THE JOURNAL OF FAMILY PRACTICE, Vol. 1, No. 2 (August) 1995, entitled "Needle Phobia: A Neglected Diagnosis", and THE JOURNAL OF AMERICAN MEDICAL ASSOCIATION, Aug./24/31, 1994 (Vol. 272, No. 8), entitled "Device-Specific Risk of Needlestick Injury in Italian Health Care Workers". THE NEW ENGLAND JOURNAL OF MEDICINE reports that the risk of percutaneous injury to health care workers causes these health care workers in the United States to receive approximately 800,000 needlesticks and related injuries from sharp objects annually. An estimated 16,000 of these devices are contaminated with human immunodeficiency virus, and even more are contaminated with hepatitis B virus or hepatitis C virus.